White-bellied Fat-tailed Mouse Opossum
Encyclopedia
The White-bellied Fat-tailed Mouse Opossum (Thylamys pallidior) is a species of opossum in the family Didelphidae. It is found in Argentina
, Bolivia
, Chile
and Peru
.
, with large ears and a narrow, pointed snout. The head and body are from 73 to 105 mm (2.9 to 4.1 in) in total length, and the tail is slightly longer, ranging from 90 to 115 mm (3.5 to 4.5 in). Adults weigh between 13 and 39 g (0.458561507366456 and 1.4 oz).
The fur on the upper parts of the animal is light cinnamon brown, while that on the underside is white or creamy, with a relatively sharp line dividing the two colors. The fur on the face is generally paler than that on the upper parts, with rings of darker, almost black, fur surrounding each eye, and sretching towards the nose. The tail is prehensile
, with only sparse hairs, albeit in a similar color to those on the body. The tail becomes noticeably thicker, especially at the base, during the autumn, when the animal lays down fat reserves in preparation for winter. The fur on the feet is white, and relatively dense about the ankles.
and south-western Bolivia
, in the northernmost regions of Chile
, and along the eastern slopes of the Andes
mountains in western and central Argentina
. It inhabits arid and semi-arid environments from sea level to 4500 metres (14,763.8 ft), ranging from the coastal deserts of Peru, through the Andes and the Monte Desert
, and into the Patagonia
n steppe of Argentina. It generally inhabits rocky environments with little plant cover, but can be found in dry forest or thorn scrub.
There are no recognised subspecies.
through the winter, they do enter torpor
if temperatures fall below around 15°C, and therefore may be inactive through much of the winter period.
In the wild, they rarely drink, being able to subsist on the water in their food. They eat a wide range of insects and spiders, but prefer beetle
s, of which they may eat up to twenty a night. Although such small invertebrates compose the majority of their diet, they also eat a moderate amount of leaves and seeds, and will occasionally consume small vertebrates such as mice and lizards. Their main predators include the Barn Owl
and the Magellanic Horned Owl
.
. However, phylogenetic analysis shows that the species' closest relatives are probably the Elegant
, Common
, and Tate's Fat-tailed Mouse Opossum
s, all of which also inhabit arid environments. Although fossils are known only from the Holocene
, estimates for the divergence of the species from its closest relatives range from 2.2 to 6 million years ago.
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
, Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
.
Description
The white-bellied fat-tailed mouse opossum is a small, mouse-like marsupialMarsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
, with large ears and a narrow, pointed snout. The head and body are from 73 to 105 mm (2.9 to 4.1 in) in total length, and the tail is slightly longer, ranging from 90 to 115 mm (3.5 to 4.5 in). Adults weigh between 13 and 39 g (0.458561507366456 and 1.4 oz).
The fur on the upper parts of the animal is light cinnamon brown, while that on the underside is white or creamy, with a relatively sharp line dividing the two colors. The fur on the face is generally paler than that on the upper parts, with rings of darker, almost black, fur surrounding each eye, and sretching towards the nose. The tail is prehensile
Prehensile tail
A prehensile tail is the tail of an animal that has adapted to be able to grasp and/or hold objects. Fully prehensile tails can be used to hold and manipulate objects, and in particular to aid arboreal creatures in finding and eating food in the trees...
, with only sparse hairs, albeit in a similar color to those on the body. The tail becomes noticeably thicker, especially at the base, during the autumn, when the animal lays down fat reserves in preparation for winter. The fur on the feet is white, and relatively dense about the ankles.
Distribution and habitat
The white-bellied fat-tailed mouse oppossum is found in southern PeruPeru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
and south-western Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
, in the northernmost regions of Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, and along the eastern slopes of the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
mountains in western and central Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. It inhabits arid and semi-arid environments from sea level to 4500 metres (14,763.8 ft), ranging from the coastal deserts of Peru, through the Andes and the Monte Desert
Monte Desert
The Monte Desert is a South American desert, located within the country of Argentina. The desert lies southeast of the Atacama Desert in Chile, north of the larger Patagonian Desert, and east of the Andes.-Geography and climate:...
, and into the Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
n steppe of Argentina. It generally inhabits rocky environments with little plant cover, but can be found in dry forest or thorn scrub.
There are no recognised subspecies.
Behavior
White-bellied fat-tailed mouse opossums are nocturnal animals with good climbing abilities, although they prefer to spend most of their time on the ground. They nest in natural cavities, either in trees or shrubs, or beneath rocks. Although they do not truly hibernateHibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
through the winter, they do enter torpor
Torpor
Torpor, sometimes called temporary hibernation is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds and some mammals such as mice and bats...
if temperatures fall below around 15°C, and therefore may be inactive through much of the winter period.
In the wild, they rarely drink, being able to subsist on the water in their food. They eat a wide range of insects and spiders, but prefer beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, of which they may eat up to twenty a night. Although such small invertebrates compose the majority of their diet, they also eat a moderate amount of leaves and seeds, and will occasionally consume small vertebrates such as mice and lizards. Their main predators include the Barn Owl
Barn Owl
The Barn Owl is the most widely distributed species of owl, and one of the most widespread of all birds. It is also referred to as Common Barn Owl, to distinguish it from other species in the barn-owl family Tytonidae. These form one of two main lineages of living owls, the other being the typical...
and the Magellanic Horned Owl
Magellanic Horned Owl
The Lesser Horned Owl or Magellanic Horned Owl is a large owl of the genus Bubo found in southern South America, extending north to the central Andes...
.
Reproduction
White-bellied fat-tailed mouse opossums are believed to be able to breed up to three times a year, although most probably only give birth once or twice. The young are born in litters of up to fifteen individuals, typically during the summer months. Unlike some other marsupials, the females do not have a pouch; the teats are variable in both number and arrangement, and may not all be functional at the same time. Individuals have lived up to eighteen months in captivity.Evolution
It is closely related to T. karimiiKarimi's fat-tailed mouse opossum
Karimi's fat-tailed mouse opossum is a species of opossum in the family Didelphidae. It is endemic to central and northeast Brazil, where it is found in the cerrado and caatinga. Its head-and-body length is about 95 millimeters, and its tail length is about 72 millimeters. It is very similar to T....
. However, phylogenetic analysis shows that the species' closest relatives are probably the Elegant
Elegant Fat-tailed Mouse Opossum
The Elegant Fat-tailed Mouse Opossum is a species of opossum in the family Didelphidae. Its head-and-body length ranges from 106 to 121 millimeters. Its tail length ranges from 115 to 142 millimeters. Its tail is swollen and has fine hairs all over it. Its fur color varies, but it usually ranges...
, Common
Common Fat-tailed Mouse Opossum
The Common Fat-tailed Mouse Opossum is a species of opossum in the family Didelphidae. It occurs in Argentina, Bolivia, Brazil, and Paraguay in chaco and Andean foothill habitats. Its head-and-body length is about 75 to 120 mm, and its tail length is about 90 to 134 mm...
, and Tate's Fat-tailed Mouse Opossum
Tate's fat-tailed mouse opossum
Tate's fat-tailed mouse opossum is a species of opossum in the family Didelphidae, named after American zoologist George Henry Hamilton Tate. It is found at elevations of 300 to 3,000 m along the coast of central Peru. The species has the northernmost range of any member of its genus. It has white...
s, all of which also inhabit arid environments. Although fossils are known only from the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
, estimates for the divergence of the species from its closest relatives range from 2.2 to 6 million years ago.